title: Efficient direct ethanol production from cellulose by cellulase- and cellodextrin transporter-co-expressing Saccharomyces cerevisiae.
abstract: Efficient degradation of cellulosic biomass requires the synergistic action of the cellulolytic enzymes endoglucanase, cellobiohydrolase, and β-glucosidase. Although there are many reports describing consolidation of hydrolysis and fermentation steps using recombinant Saccharomyces cerevisiae that express cellulolytic enzymes, the efficiency of cellulose degradation has not been sufficiently improved. Although the yeast S. cerevisiae cannot take up cellooligosaccharide, some fungi can take up and assimilate cellooligosaccharide through a cellodextrin transporter. In this study, a S. cerevisiae strain co-expressing genes for several cell surface display cellulases and the cellodextrin transporter was constructed for the purpose of improving the efficiency of direct ethanol fermentation from phosphoric acid swollen cellulose (PASC). The cellulase/cellodextrin transporter-coexpressing strain produced 1.7-fold more ethanol (4.3 g/L) from PASC during a 72-h fermentation than did a strain expressing cellulase only (2.5 g/L). Direct ethanol production from PASC by the recombinant S. cerevisiae strain was improved by co-expression of cellulase display and cellodextrin transporter genes. These results suggest that cellulase- and cellodextrin transporter-co-expressing S. cerevisiae could be a promising technology for efficient direct ethanol production from cellulose.
authors.affiliation: Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe, Hyogo 657-8501, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Yamada
authors.affiliation: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe, Hyogo 657-8501, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Nakatani
authors.affiliation: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe, Hyogo 657-8501, Japan.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Ogino
authors.affiliation: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe, Hyogo 657-8501, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kondo
keywords: Bioethanol; Cell surface display; Cellodextrin transporter; Cellulase; Cellulose; Yeast